An automatic sprinkler system is one of the most widely used devices for fire protection. These systems have sprinklers that are activated once the ambient temperature in an environment, such as a room or building exceeds a predetermined value. Once activated, the sprinklers distribute fire-extinguishing fluid, preferably water, in the room or building. A sprinkler system is considered effective if it extinguishes or prevents growth of a fire. Failures of such systems may occur when the system has been rendered inoperative during building alternation or disuse, or the occupancy hazard has been increased beyond initial system capability.
The water supply for a sprinkler system may be separate from that used by a fire department. An underground main for the sprinkler system enters the building to supply a riser. Connected at the riser are valves, meters, and, preferably, an alarm to sound when water flow within the system exceeds a predetermined minimum. At the top of a vertical riser, a horizontally disposed array of pipes extends throughout the fire compartment in the building. Other risers may feed distribution networks to systems in adjacent fire compartments. Compartmentalization can divide a large building horizontally, on a single floor, and, vertically, floor to floor. Thus, several sprinkler systems may serve one building.
In the piping distribution network, branch lines carry the sprinklers. A sprinkler may extend up from a branch line, placing the sprinkler relatively close to the ceiling, or a sprinkler can be pendant below the branch line. For use with concealed piping, a flush-mounted pendant sprinkler may extend only slightly below the ceiling.
Water for fighting a fire can be provided to the sprinklers in various configurations. In a wet-pipe system, for buildings having heated spaces for piping branch lines, all the system pipes contain water for immediate release through any sprinkler that is activated. In a dry-pipe system, which may include pipes, risers, and feed mains, disposed in unheated open areas, cold rooms, passageways, or other areas exposed to freezing temperatures, such as unheated buildings in freezing climates or cold-storage rooms, branch lines and other distribution pipes may contain a dry gas (air or nitrogen) under pressure. This pressure of gas holds closed a dry pipe valve at the riser. When heat from a fire activates a sprinkler, the gas escapes and the dry-pipe valve trips, water enters branch lines, and fire fighting begins as the sprinkler distributes the water.
Dry sprinklers are used where the sprinklers may be exposed to freezing temperatures. A dry sprinkler may include a threaded inlet containing a closure assembly, some length of tubing connected to the threaded inlet, and a fluid deflecting structure located at the other end of the tubing. There may also be a mechanism that connects the thermally responsive component to the closure assembly. The threaded inlet is preferably secured to a branch line. Depending on the particular installation, the branch line may be filled with fluid (wet pipe system) or be filled with a gas (dry pipe system). In either installation, the medium within the branch line is generally excluded from the tubing of the dry sprinkler via the closure assembly until activation of the thermally responsive component. In some dry sprinklers, when the thermally responsive component releases, the closure assembly or portions of the mechanism may be expelled from the tubing of the dry sprinkler by water pressure and gravity. In other types of dry sprinklers, the closure assembly is pivotally mounted to a movable mechanism that is a tube structure, and the closure assembly is designed to pivot on a pin pivot axis transverse to the longitudinal axis of the dry sprinkler, while the tube structure is maintained within the tubing of the dry sprinkler.
In known dry sprinklers, a metallic disc annulus has been provided as a component of a closure assembly to seal the inlet of the dry sprinkler. The metallic disc annulus has a face disposed about a central axis between an inner perimeter and outer perimeter. When the dry sprinkler is in an unactuated condition, the central axis of the metallic disc annulus is generally parallel and aligned with the longitudinal axis of the tubing. Upon actuation of the dry sprinkler, the metallic disc annulus provides an axial thrust force to assist in the movement of the closure assembly along the longitudinal axis of the tubing.
In order to utilize the metallic disc annulus, an arrangement of components is provided within the known dry sprinklers. This arrangement of components positions the metallic disc annulus within the passageway defined by the tube structure to prohibit and allow fluid flow through the dry sprinkler. The metallic disc annulus is positioned at the inlet to provide a seal of the inlet, and within the passageway to permit flow through the dry sprinkler. When the metallic disc annulus is positioned to occlude the inlet, the arrangement of components orients the central axis of the metallic disc annulus generally parallel to and aligned with the longitudinal axis. When the metallic disc annulus is positioned within the passage to allow flow through the outlet of the dry sprinkler, the arrangement of components translates the metallic disc annulus along the passageway.
Although the known dry sprinklers have employed a metallic disc annulus to utilize the axial thrust that it creates to translate the closure assembly within the passageway, the arrangement of components, including the metallic disc annulus, has been found to be inadequate for the performance of the dry sprinkler Specifically, the inventors have discovered that the known arrangements of components translate the metallic disc annulus along the passageway, however, these arrangements of components appear to maintain an orientation of the central axis of the metallic disc annulus along the longitudinal axis of the dry sprinkler such that the known dry sprinklers fail to achieve their expected performance.
In particular, the inventors have discovered that the known dry sprinklers fail to provide a flow rate at an expected level of tolerance based on the discharge coefficient for which the known sprinklers purport to provide at various pressures provided to the inlet prior to actuation of the dry sprinkler (i.e., start pressures) between 0 and 175 psig. That is, as these known dry sprinklers are rated for a particular discharge coefficient, which is specified as a rated K-factor, the known dry sprinklers should provide an expected flow rate based on the rated K-factor. Here, the rated K-factor defines the expected flow of fluid in gallons per minute from an outlet of the dry sprinkler divided by the square root of the pressure of the flow of fluid fed into the inlet of the dry sprinkler in pounds per square inch gauge. Based on the rated K-factor, the known dry sprinklers should provide the expected flow rate from an outlet of the known dry sprinklers within an acceptable tolerance level when a specified pressure of fluid flow is applied to the inlet of the known dry sprinklers. The known dry sprinklers, however, provide an actual flow rate from the outlet at less than an acceptable tolerance level. Thus, the known dry sprinklers fail to provide an arrangement of components that allow for the metallic disc annulus to translate along the passageway into an orientation where the central axis of the metallic disc annulus is skewed to the longitudinal axis within the passageway so that a flow of fluid in gallons per minute from the outlet of the structure is at an acceptable level, such as at least 95 percent of the rated K-factor multiplied by the square root of the pressure of the flow of fluid fed into the inlet of the structure in pounds per square inch gauge.